Process for producing stencil printing sheet

Abstract: A process for producing a stencil printing sheet, in which the production of the stencil printing sheet is easy, a production cost thereof is reduced and there is no generation of any perforating failure at a time of plate-making, any wrinkles, any conveying failure and any printing failure, was disclosed. The process for producing the stencil printing sheet comprises the steps of laminating a solvent-soluble resin layer formed on a nonadhesive substrate to a porous substrate with an adhesive or by heat-adhesion, and then, removing the nonadhesive substrate described above from the solvent-soluble resin layer described above.

Description: The present invention relates to a process for producing a stencil printing sheet. Specifically, the present invention relates to a process for producing a stencil printing sheet having a solvent-soluble resin layer. In the prior art, a heat-sensitive stencil sheet is known which is produced by laminating a thermoplastic resin film onto a porous substrate with an adhesive. Stencil-making of this heat-sensitive stencil sheet is carried out by means of (1) a process of superposing a hand written or preliminarily prepared manuscript onto a heat-sensitive stencil sheet and then perforating by melting the thermoplastic resin film using the heat generated from, for example, a flash lamp or an infrared lamp (see for example US-A-4628813); and (2) a process of bringing a thermal head which generates dot-like heat zones in accordance with electrical signals from letter or picture information, into contact with a heat-sensitive stencil sheet, and perforating by melting the thermoplastic resin film (see for example US-A-4568951). However, the stencil-making processes described above require a complicated process of bringing either a manuscript heated by irradiated light or a thermal head into contact with a heat-sensitive stencil sheet, conducting the heat to the thermoplastic resin film of the heat-sensitive stencil sheet to melt the thermoplastic resin film and then shrinking the molten material to perforate the thermoplastic resin film. These stencil-making processes have the disadvantage that, for example, (1) a perforating failure is produced on contact failure between a thermoplastic resin film and a manuscript which has absorbed heat of a thermal head; (2) a perforating failure is produced by non-uniformity in the applied pressure of a thermal head, resulting in wrinkles in a heat-sensitive stencil sheet; (3) the molten material of a thermoplastic resin film was adhered to a thermal head, resulting in a conveying failure of heat-sensitive stencil sheet; and (4) since the molten material is left in a perforated portion, ink permeability is prevented, resulting in printing failure. In recent years, a further improvement in quality of heat-sensitive stencil sheet is demanded. It is demanded to provide such a heat-sensitive stencil sheet that satisfies the smoothness of a thermoplastic resin film, the separating property of the thermoplastic resin film from the manuscript or thermal head, the melting property due to heat and the shrinkability of a thermoplastic resin film heat, the adhesive strength between a thermoplastic resin film and a porous substrate, and the mechanical strength and abrasion of the porous substrate, and therefore, the condition for producing heat-sensitive stencil sheet becomes complicated and there was the problem that the production cost was accordingly increased. GB-A-255361 discloses the production of stencils which includes securing, during the local application of a liquefying agent to a stencil sheet, intimate contact between the back of the stencil sheet and a porous or absorbent support or backing. JP-A-62-173296 discloses the production of thermal stencil paper through perforation in which a solution of a thermoplastic resin is applied to a releasable tentative base and a porous base is adhered to the resin film through the adhesive layer. It is a main aim of this invention to solve the above-mentioned problems in the prior art and provide a process for producing a stencil printing sheet in which the production process is easy, the production cost can be lowered and there are no perforating failure at a time of stencil-making, no generation of wrinkles, no conveying failure and no printing failure. Accordingly, the present invention provides a process for producing a stencil printing sheet, comprising the steps of: laminating a resin layer formed on a non-adhesive substrate to a porous substrate with an adhesive or by heat-adhesion; and removing said non-adhesive substrate from said resin layer to obtain a stencil printing sheet; characterized in that said resin layer is water-soluble and in that said process further comprises the step of perforating said water-soluble resin layer by the application of a solvent containing water onto said water soluble resin layer. A preferred embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:- FIGS. 1A-1C are explanatory view of steps in the process for producing a stencil printing sheet according to the present invention; and FIG. 2 is an explanatory view showing the perforation of a stencil printing sheet obtained by the process of the present invention. A water-soluble resin layer to be used in this invention is formed on a non-adhesive substrate and contains a thermoplastic or thermosetting resin soluble in water as a main component. As a water-soluble resin, a resin soluble in a water or in a water-miscible solvent, such as polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, polyvinyl pyrolidone, polyethylene-polyvinyl alcohol copolymer, polyethylene oxide, polyvinyl ether, polyvinyl acetal, polycarylamide, starch, dextrin, alginic acid, ascorbic acid or water-soluble urethane, may be used. These resins may be used independently or in admixture. Copolymerized forms of these resins may also be used. In addition to the above resin components, dyestuffs, pigments, fillers, binders and hardeners may also be contained in the resin layer. The thickness of the resin layer formed on a non-adhesive substrate in preferably in the range of from 0.1µm to 100µm, and more preferably in the range of from 1µm to 50µm. When the thickness is less than 0.1µm the strength of the resin layer is insufficient and when the thickness exceeds 100µm a large quantity of solvent may be required to perforate the resin layer and the perforation of the resin layer is often insufficient. There is no particular limitation to the non-adhesive substrate that can be used in the present invention. For example, a silicone-treated separation sheet, polyester film, polytetrafluoroethylene sheet or polypropylene film may be used. A thin resin layer of low mechanical strength can be laminated onto a porous substrate easily by mounting the resin layer on a non-adhesive substrate in advance. When the thickness of the water-soluble resin layer to be laminated to the porous substrate is thin, the amount of the solvent to be used at the time of stencil-making may be small. Not only is the use of a small amount of solvent economical but the time required for stencil-making can be shortened. In addition, a resin layer of low mechanical strength can be handled easily during production. Furthermore, the surface characteristics of the resin layer can be altered by changing the surface property of the non-adhesive substrate. In the stencil-making and printing processes, when a non-adhesive substrate having a rough surface is used, the rough surface is transcribed onto the water-soluble resin layer, and as a result various effects such as an improvement in the conveying property during stencil-making of the stencil printing sheet can be obtained. As a porous substrate to be used in the invention, Japanese paper, woven or non-woven cloth, gauze made from natural fiber such as Manila hemp, pulp, Mitsumata (Edgeworthia papyrifera Sieb.), Kozo (Broussonetia kazinoki Sieb.), synthetic fiber such as polyester, nylon, vinylon, acetate fiber or a thin leaf paper of metallic fiber or glass fiber, independently or in admixture, are examples. The basis weight of the porous substrate is preferable in the range of from 1g/m 2 to 20g/m 2 , and more preferably in the range of from 5g/m 2 to 15g/m 2 . When the basis weight is less than 1g/m 2 the strength of the sheet is weak, and when the basis weight exceeds 20g/m 2 the ink permeability is often poor at the time of printing. Also, the thickness of the porous substrate is preferably in the range of from 5µm to 100µm, and more preferably in the range of from 10µm to 50µm. When the thickness is less than 5µm the strength of the sheet is weak, and when the thickness exceeds 100µm the ink permeability at the time of printing is often poor. Now, a detailed description of the process for producing a stencil printing sheet according to the present invention will be given. First of all, a resin solution is prepared by dissolving a water-soluble resin in a solvent. This solvent may be the same as or different from the solvent used for the stencil-making of stencil printing sheet which will be described later. However, from the viewpoint of production efficiency, it is preferable to use a solvent which dries readily. The viscosity and surface tension of the resin solution are properly controlled while taking the coating condition to a non-adhesive substrate into consideration. Then, the above-mentioned resin solution is coated on a non-adhesive substrate by means of, for example, a roller coater, photogravure coater, wire bar coater, reverse coater, and dried to form a water-soluble resin layer. Subsequently, the water-soluble resin layer formed on the non-adhesive substrate is laminated to a porous substrate. As a laminating process, a process of (1) using an adhesive, and (2) heat-adhering a resin layer and porous substrate, can be adapted. In the case of the process (1), a solvent-soluble type or water-dispersion type adhesive is coated on to a resin layer or porous substrate and then cured thermally or photolytically for lamination. Heat-adhesion may be performed using a hot-melt type adhesive for lamination. As an adhesive, the coated film after curing is preferably water soluble. For example, epoxy resin, phenolic resin, vinyl acetate, ethylene-vinyl acetate copolymer, vinyl chloride-vinyl acetate copolymer, acrylic resin, polyester, polyurethane, styrene-butadiene copolymer, polyisobutylene, isoprene, butyl rubber, polyacrylamide, rosin, terpene or polystyrene can be used. Also, a hardener, softener, adhesive adder or filler may be mixed therewith, if necessary. The process (2) can be employed when a thermally meltable component is contained in the resin layer and/or the porous substrate. In this case, the resin layer can be laminated to the porous substrate by means of a heating apparatus such as a heat roller. Subsequently, the non-adhesive substrate laminated to the water-soluble resin layer is peeled off to give a stencil printing sheet. Figs. 1A, 1B and 1C show a process for producing a stencil printing sheet using an adhesive. In Fig. 1A, a water-soluble resin layer 1 is formed on a non-adhesive substrate 2, and in Fig. 1B, a porous substrate 3 is impregnated with an adhesive to form an adhesive layer 4. In Fig. 1C, the adhesive layer 4 is laminated to the above water-soluble resin layer 1 and after then, the non-adhesive substrate 2 is removed from the water-soluble resin layer 1. Since the above stencil printing sheet has a water-soluble resin layer, in the case of bringing it in contact with a solvent which dissolves the resin layer, the resin in its contact portion starts dissolving into the solvent, and the resin dissolves into the solvent up to its saturation in solubility. The solution which dissolved the resin permeates into a porous substrate and the resin layer corresponding to this portion is perforated. Since the solution which was dissolved in the resin layer permeates into the porous substrate, the dissolved component is not left in the perforated portion of the resin layer and does not obstruct the perforation. In addition, the perforating property of the resin layer can be adjusted by controlling the solubility of the solvent to the resin layer and the quantity of the contacting solvent. Dyestuffs, pigments, fillers, binders, hardeners, antiseptics, wetting agents, surfactants and pH conditioners can be contained in the solvent. Fig. 2 shows an explanatory view of a process for stencil-making using the above stencil printing sheet. In the drawing, a solvent 6 is ejected from a solvent ejecting means 10 and brought in contact with the surface of the water-soluble resin layer 1 of a stencil printing sheet 5. A contacting solvent 7 dissolves the resin and adhesive layer 4 in the contacted portion. The dissolving solution 8 permeates into the interior of the porous substrate to perforate the contacted portion. Numeral 9 shows a perforated resin layer. As for a solvent feed process, it may be carried out by bringing a means, such as a brush pen immersed into a solvent, in contact with a water-soluble resin layer directly, but it is preferably to feed the solvent to the resin layer in a non-contact condition by a solvent ejecting device. As for this kind of solvent ejecting device, there is exemplified such an apparatus that a nozzle, a slit, an injector, a porous material, or a porous film is connected to a liquid feed pump, a piezoelectric element or a heating element so as to release the solvent intermittently or continuously in a dot or a line pattern corresponding to each letter and picture signal. Since this kind of process makes it possible to carry out the stencil-making of stencil printing sheets in a non-contact condition with a stencil-making apparatus, there is no generation of wrinkles at a time of stencil-making. Also, differently from a conventional heat-sensitive stencil sheet, no molten material is left in the perforated portion and a brilliant printed matter can be obtained. Furthermore, the stencil printing sheet of the invention can be produced easily without any needs of separating property, abrasion and mechanical strength as required in the conventional heat-sensitive stencil sheet. The stencil printing sheet obtained by the process of the invention can be applied to a general stencil printing process to obtain a printed matter. For example, a printed matter can be obtained by mounting an ink on a perforated stencil printing sheet, passing the ink through each portion perforated by press rolls, reduced pressure means or squeegee rolls, and transcribing the ink to a printing paper. As a printing in, an oily ink usually used in stencil printing, a water-based ink, a water-in-oil emulsion ink or an oil-in-water emulsion ink can be used. A more detailed described of the present invention will now be given with reference to the following Examples. It should be understood, however, that these Examples are not intended to limit the scope of the claimed invention. EXAMPLE 1 (1) Production of Stencil Printing Sheet A resin solution consisting of the following composition was coated by a reverse coater on a silicone-treated polyester film of 30µm in thickness and dried to form a water-soluble resin layer of 3µm in thickness thereon. Polyethylene oxide 15 parts by weight Isopropyl alcohol 15 parts by weight Water 70 parts by weight Then, after a polyester fiber cloth having a sieve opening of 300 mesh was immersed in an adhesive solution consisting of the following composition, it was taken out and dried. The water-soluble resin layer formed on the polyester film described above was superposed and laminated to the surface of this polyester cloth and left in a thermostat over night. Acrylic resin 20 parts by weight Isocyanate 5 parts by weight Toluene 45 parts by weight Ethyl acetate 30 parts by weight Subsequently, the resulting polyester film was removed from the resin layer to give a stencil printing sheet. (2) Stencil-making by Stencil Printing Sheet and Stencil Printing Then, the ink in the ink jet printer was replaced with a mixed solvent consisting of the following composition, and the mixed solvent was ejected from the nozzle of the ink jet printer to the stencil printing sheet described above corresponding to the letters and pictures composed by a personal computer. The resin layer at the ejected portion was dissolved to perforate the stencil printing sheet. Isopropyl alcohol 30 parts by weight Diethylene glycol 10 parts by weight Water 60 parts by weight. A black offset ink was mounted on the polyester fiber cloth of the stencil printing sheet of stencil-making described above and this was superposed on the printing paper. When the ink was squeezed by a blade, brilliant letters and pictures similar to those produced by an ink jet printer could be obtained. EXAMPLE 2 (1) Production of Stencil Printing Sheet A resin solution consisting of the following composition was coated by a reverse coater on a polypropylene film of 40µm in thickness and then, dried to form a water-soluble resin layer of 3µm in thickness thereon. Polyvinyl ether 15 parts by weight Methyl alcohol 15 parts by weight Water 70 parts by weight Then, a polyester fiber cloth having a sieve opening of 300 mesh was superposed on the polyvinyl ether resin layer of the polypropylene film described above and laminated to it by passing the polypropylene film through heat rollers at 120°C. Subsequently, the resulting polypropylene film was removed from the resin layer to give a stencil printing sheet. (2) Stencil-making by Stencil Printing Sheet and Stencil Printing In the similar manner as shown in Example 1, stencil-making and printing operations were carried out using the stencil printing sheet described above to give a good printed matter. According to the production process of the invention, as a water-soluble resin layer having a thin thickness can be laminated to a porous substrate, the resulting production costs can be reduced. That is, as the resin layer is laminated on a non-adhesive substrate in advance, a resin layer having a thin thickness and a weak strength can be used. Thus, an amount of the solvent and a time for the stencil-making can be saved. Since the stencil printing sheet obtained by the production process of the invention can be perforated by a solvent in its non-contact condition, there is no generation of any perforating failure at a time of stencil-making, any wrinkles and conveying failure, resulting in obtaining brilliantly printed pictures thereby.

Claims: A process for producing a stencil printing sheet (5), comprising the steps of: laminating a resin layer (1) formed on a non-adhesive substrate (2) to a porous substrate (3) with an adhesive (4) or by heat-adhesion; and removing said non-adhesive substrate (2) from said resin layer (1) to obtain a stencil printing sheet; characterized in that said resin layer (1) is water-soluble and in that said process further comprises the step of perforating said water-soluble resin layer (1) by the application of a solvent containing water onto said water soluble resin layer (1). A process for producing a stencil printing sheet according to claim 1, wherein said water-soluble resin is selected from polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, polyvinyl pyrolidone, polyethylene-polyvinyl alcohol copolymer, polyethylene oxide, polyvinyl ether, polyvinyl acetal, polyacrylamide, starch, dextrin, alginic acid, ascorbic acid or water-soluble urethane. A process for producing a stencil printing sheet according to claim 1, wherein said water-soluble resin layer (1) has a thickness in the range of from 0.1 to 100µm. A process for producing a stencil printing sheet according to claim 1, wherein said porous substrate (3) is selected from a polyester fiber cloth or a Japanese paper having a basis weight in the range of from 1 to 20 g/m 2 and a thickness in the range of from 5 to 100µm.

Inventors: WATANABE HIDEO, WATANABE, HIDEO, WATANABE, HIDEO, RISO KAGAKU CORPORATION
Applicants: RISO KAGAKU CORP, RISO KAGAKU CORPORATION
Application year: 1994
Main classification: B41N1
IPC codes: B41N1, B41C1